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著者人数: 14名, 形態: カラー図版あり, Number of authors: 14, Physical characteristics: Original contains color illustrations, Accepted: 2021-06-21, 資料番号: PA2210071000

The thermal infrared nadir spectra of IASI (Infrared Atmospheric Sounding Interferometer) are successfully used for retrievals of different atmospheric trace gas profiles. However, these retrievals offer generally reduced information about the lowermost tropospheric layer due to the lack of thermal contrast close to the surface. Spectra of scattered solar radiation observed in the near-infrared and/or shortwave infrared, for instance by TROPOMI (TROPOspheric Monitoring Instrument), offer higher sensitivity near the ground and are used for the retrieval of total-column-averaged mixing ratios of a variety of atmospheric trace gases. Here we present a method for the synergetic use of IASI profile and TROPOMI total-column level 2 retrieval products. Our method uses the output of the individual retrievals and consists of linear algebra a posteriori calculations (i.e. calculation after the individual retrievals). We show that this approach has strong theoretical similarities to applying the spectra of the different sensors together in a single retrieval procedure but with the substantial advantage of being applicable to data generated with different individual retrieval processors, of being very time efficient, and of directly benefiting from the high quality and most recent improvements of the individual retrieval processors. We demonstrate the method exemplarily for atmospheric methane (CH4). We perform a theoretical evaluation and show that the a posteriori combination method yields a total-column-averaged CH4 product (XCH4) that conserves the good sensitivity of the corresponding TROPOMI product while merging it with the high-quality upper troposphere–lower stratosphere (UTLS) CH4 partial-column information of the corresponding IASI product. As a consequence, the combined product offers additional sensitivity for the tropospheric CH4 partial column, which is not provided by the individual TROPOMI nor the individual IASI product. The theoretically predicted synergetic effect is verified by comparisons to CH4 reference data obtained from collocated XCH4 measurements at 14 globally distributed TCCON (Total Carbon Column Observing Network) stations, CH4 profile measurements made by 36 individual AirCore soundings, and tropospheric CH4 data derived from continuous ground-based in situ observations made at two nearby Global Atmospheric Watch (GAW) mountain stations. The comparisons clearly demonstrate that the combined product can reliably detect the actual variations of atmospheric XCH4, CH4 in the UTLS, and CH4 in the troposphere. A similar good reliability for the latter is not achievable by the individual TROPOMI and IASI products.

International audience; Abstract. In this study, an extension on the previously reported status of the COllaborative Carbon Column Observing Network's (COCCON) calibration procedures incorporating refined methods is presented. COCCON is a global network of portable Bruker EM27/SUN FTIR spectrometers for deriving column-averaged atmospheric abundances of greenhouse gases. The original laboratory open-path lamp measurements for deriving the instrumental line shape (ILS) of the spectrometer from water vapour lines have been refined and extended to the secondary detector channel incorporated in the EM27/SUN spectrometer for detection of carbon monoxide (CO). The refinements encompass improved spectroscopic line lists for the relevant water lines and a revision of the laboratory pressure measurements used for the analysis of the spectra. The new results are found to be in good agreement with those reported by Frey et al. (2019) and discussed in detail. In addition, a new calibration cell for ILS measurements was designed, constructed and put into service. Spectrometers calibrated since January 2020 were tested using both methods for ILS characterization, open-path (OP) and cell measurements. We demonstrate that both methods can detect the small variations in ILS characteristics between different spectrometers, but the results of the cell method indicate a systematic bias of the OP method. Finally, a revision and extension of the COCCON network instrument-to-instrument calibration factors for XCO2, XCO and XCH4 is presented, incorporating 47 new spectrometers (of 83 in total by now). This calibration is based on the reference EM27/SUN spectrometer operated by the Karlsruhe Institute of Technology (KIT) and spectra collected by the collocated TCCON station Karlsruhe. Variations in the instrumental characteristics of the reference EM27/SUN from 2014 to 2017 were detected, probably arising from realignment and the dual-channel upgrade performed in early 2018. These variations are considered in the evaluation of the instrument-specific calibration factors in order to keep all tabulated calibration results consistent.

Intensive coal mining activities are in the Upper Silesian Coal Basin (USCB) in southern Poland, resulting in large amounts of methane (CH4) emissions. Annual CH4 emission reached to 448 kt according to the European Pollutant Release and Transfer Register (E-PRTR, 2017). As a CH4 emission hot spot in Europe, it is of importance to investigate its emission sources and accurate emission estimates. In this study, we use satellite-based column-averaged dry-air molar fraction observations of CH4 (XCH4) from the TROPOspheric Monitoring Instrument (TROPOMI) and tropospheric XCH4 (TXCH4) from the Infrared Atmospheric Sounding Interferometer (IASI), together with the high-resolution model forecast XCH4 and TXCH4 from the Copernicus Atmosphere Monitoring Service (CAMS) to estimate the CH4 emission rate averaged over three years in the USCB region (49.3°–50.8° N and 18°–20° E). Using the CAMS inventory as the a priori knowledge of the sources, together with ERA5 wind at 330 m, the wind-assigned XCH4 anomalies for two opposite wind directions are calculated, which yields an estimated CH4 emission of 9.6E26 ± 1.4E25 molec./s for CAMS XCH4 and 9.1E26 ± 1.2E25 molec./s for CAMS TXCH4. These values are very close to the total emission of the CAMS inventory (9.7E26 molec./s). Very good agreements between CAMS and the wind-assigned model results (R2 = 0.89 for XCH4 and TXCH4) indicate that our wind-assigned method is quite robust. The similar estimates of XCH4 and TXCH4 also imply that for a strong source, the dynamically induced variations of the CH4 mixing ratio in the upper troposphere and lower stratosphere region is of secondary importance. This wind-assigned method is further applied to the TROPOMI XCH4 and TROPOMI+IASI TXCH4 with using the Carbon dioxide and Methane (CoMet) inventory performed in 2018. The calculated averaged total CH4 emission over the USCB region is about 5.7E26 ± 4.9E24 molec./s for TROPOMI XCH4 and 5.2E26 ± 2.2E25 molec./s for TROPOMI+IASI TXCH4. These results are very close and thus in agreement to the emissions given in the E-PRTR inventory (5.33E26 molec./s) and the CoMet inventory (6.6E26 molec./s). Since the wind speed is increasing with altitude, sensitivity tests show that higher CH4 emission strengths are yielded with increasing altitude and vice versa. About 23 % lower and 13 % higher estimates are obtained when using lower wind information at 10 m and higher wind information at 500 m instead of 330 m, respectively. When using different wind coverage and different wind segmentation, an uncertainty of 4.2 % and −2.1% is obtained, respectively. These results suggest that our wind-assigned method is quite robust and might also serve as a simple method to estimate CH4 or CO2 emissions for other regions.

Intensive coal mining activities in the Upper Silesian Coal Basin (USCB) in southern Poland are resulting in large amounts of methane (CH4) emissions. Annual CH4 emissions reached 448 kt according to the European Pollutant Release and Transfer Register (E-PRTR, 2017). As a CH4 emission hotspot in Europe, it is of importance to investigate its emission sources and make accurate emission estimates. In this study, we use satellite-based total column-averaged dry-air mole fraction of CH4 (XCH4) from the TROPOspheric Monitoring Instrument (TROPOMI) and tropospheric XCH4 (TXCH4) from the Infrared Atmospheric Sounding Interferometer (IASI). In addition, the high-resolution model forecasts, XCH4 and TXCH4, from the Copernicus Atmosphere Monitoring Service (CAMS) are used to estimate the CH4 emission rate averaged over 3 years (November 2017–December 2020) in the USCB region (49.3–50.8∘ N and 18–20∘ E). The wind-assigned anomaly method is first validated using the CAMS forecast data (XCH4 and TXCH4), showing a good agreement with the CAMS GLOBal ANThropogenic emission (CAMS-GLOB-ANT) inventory. It indicates that the wind-assigned method works well. This wind-assigned method is further applied to the TROPOMI XCH4 and TROPOMI + IASI TXCH4 by using the Carbon dioxide and Methane (CoMet) inventory derived for the year 2018. The calculated averaged total CH4 emissions over the USCB region is about 496 kt yr−1 (5.9×1026 molec. s−1) for TROPOMI XCH4 and 437 kt yr−1 (5.2×1026 molec. s−1) for TROPOMI + IASI TXCH4. These values are very close to the ones given in the E-PRTR inventory (448 kt yr−1) and the ones in the CoMet inventory (555 kt yr−1), and are thus in agreement with these inventories. The similar estimates of XCH4 and TXCH4 also imply that for a strong source, the dynamically induced variations of the CH4 mixing ratio in the upper troposphere and lower stratosphere region are of secondary importance. Uncertainties from different error sources (background removal and noise in the data, vertical wind shear, wind field segmentation, and angle of the emission cone) are approximately 14.8 % for TROPOMI XCH4 and 11.4 % for TROPOMI + IASI TXCH4. These results suggest that our wind-assigned method is quite robust and might also serve as a simple method to estimate CH4 or CO2 emissions for other regions.

In this study, an extension on the previously reported status of the COllaborative Carbon Column Observing Network’s (COCCON) calibration procedures incorporating refined methods is presented. COCCON is a global network of portable Bruker EM27/SUN FTIR spectrometers for deriving column-averaged atmospheric abundances of greenhouse gases. The original laboratory open-path lamp measurements for deriving the instrumental line shape (ILS) of the spectrometer from water vapour lines have been refined and extended to the secondary detector channel incorporated in the EM27/SUN spectrometer for detection of carbon monoxide (CO). The refinements encompass improved spectroscopic line lists for the relevant water lines and a revision of the laboratory pressure measurements used for the analysis of the spectra. The new results are found to be in good agreement with those reported by Frey et al. (2019), and discussed in detail. In addition, a new calibration cell for ILS measurements was designed, constructed and put into service. Spectrometers calibrated since January 2020 were tested using both methods for ILS characterisation, open path (OP) and cell measurements. We demonstrate that both methods can detect the small variations of ILS characteristics between different spectrometers, but the results of the cell method indicate a systematic bias of the OP method. Finally, a revision and extension of the COCCON network instrument-to-instrument calibration factors for XCO2, XCO, and XCH4 is presented, incorporating 47 new spectrometers (of 83 in total by now). This calibration is based on the reference EM27/SUN spectrometer operated by the Karlsruhe Institute of Technology (KIT) and spectra collected by the collocated TCCON station Karlsruhe. Variations in the instrumental characteristics of the reference EM27/SUN during 2014 to 2017 were detected probably arising from realignment and the dual-channel upgrade performed in early 2018. These variations are considered in the evaluation of the instrument-specific calibration factors in order to keep all tabulated calibration results consistent.

We use different methane ground- and space-based remote sensing data sets for investigating the emission strength of three waste disposal sites close to Madrid. We present a method that uses wind-assigned anomalies for deriving emission strengths from satellite data and estimating their uncertainty to 9–14 %. The emission strengths estimated from the remote sensing data sets are significantly larger than the values published in the official register. ESA support through the COCCON-PROCEEDS and COCCON-PROCEEDS II projects. In addition, this research was funded by the Ministerio de Economía y Competitividad from Spain through the INMENSE project (CGL2016-80688-P). This research has largely benefit from funds of the Deutsche Forschungsgemeinschaft (provided for the two projects MOTIV and TEDDY with IDs/290612604 and 416767181, respectively).

Methane (CH4) emissions from coal production amount to roughly one-third of European anthropogenic CH4 emissions in the atmosphere. Poland is the largest hard coal producer in the European Union with the Polish side of the Upper Silesian Coal Basin (USCB) as the main part of it. Emission estimates for CH4 from the USCB for individual coal mine ventilation shafts range between 0.03 and 20 kt a−1, amounting to a basin total of roughly 440 kt a−1 according to the European Pollutant Release and Transfer Register (E-PRTR, http://prtr.ec.europa.eu/, 2014). We mounted a ground-based, portable, sun-viewing FTS (Fourier transform spectrometer) on a truck for sampling coal mine ventilation plumes by driving cross-sectional stop-and-go patterns at 1 to 3 km from the exhaust shafts. Several of these transects allowed for estimation of CH4 emissions based on the observed enhancements of the column-averaged dry-air mole fractions of methane (XCH4) using a mass balance approach. Our resulting emission estimates range from 6±1 kt a−1 for a single shaft up to 109±33 kt a−1 for a subregion of the USCB, which is in broad agreement with the E-PRTR reports. Three wind lidars were deployed in the larger USCB region providing ancillary information about spatial and temporal variability of wind and turbulence in the atmospheric boundary layer. Sensitivity studies show that, despite drawing from the three wind lidars, the uncertainty of the local wind dominates the uncertainty of the emission estimates, by far exceeding errors related to the XCH4 measurements themselves. Wind-related relative errors on the emission estimates typically amount to 20 %.

Methane (CH4) emissions from coal production are one of the primary sources of anthropogenic CH4 in the atmosphere. Poland is the largest hard coal producer in the European Union with the Polish side of the Upper Silesian Coal Basin (USCB) as the main part of it. Emission estimates for CH4 from the USCB for individual coal mine ventilation shafts range between 0.03 kt/a and 20 kt/a, amounting to a basin total of roughly 440 kt/a according to the European Pollutant Release and Transfer Register (E-PRTR, http://prtr.ec.europa.eu/, 2014). We mounted a ground-based, portable, sun-viewing FTS (Fourier Transform Spectrometer) on a truck for sampling coal mine ventilation plumes by driving cross-sectional stop-and-go Patterns at 1 to 3 km distance to the exhaust shafts. Using a mass balance approach, several of these transects allowed for estimating CH4 emissions based on the observed enhancements of the column-averaged dry-air mole fractions of methane (XCH4). Our resulting emission estimates range from 6 ± 1 kt/a for a single shaft up to 109 ± 33 kt/a for a subregion of the USCB, which is in broad agreement with the E-PRTR reports. Three wind lidars were deployed in the larger USCB region providing ancillary information about spatial and temporal variability of wind and turbulence in the atmospheric boundary-layer. Sensitivity studies show that, despite drawing from the three wind lidars, the uncertainty of the local wind dominates the uncertainty of the emission estimates, by far exceeding errors related to the XCH4 measurements itself. Wind-related relative errors on the emission estimates typically amount to 20 %.

We report on the ground-based FTIR (Fourier transform infrared) tropospheric water vapour isotopologue remote sensing data that have been recently made available via the database of NDACC (Network for the Detection of Atmospheric Composition Change; ftp://ftp.cpc.ncep.noaa.gov/ndacc/MUSICA/) and via doi:10.5281/zenodo.48902. Currently, data are available for 12 globally distributed stations. They have been centrally retrieved and quality-filtered in the framework of the MUSICA project (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water). We explain particularities of retrieving the water vapour isotopologue state (vertical distribution of H216O, H218O, and HD16O) and reveal the need for a new metadata template for archiving FTIR isotopologue data. We describe the format of different data components and give recommendations for correct data usage. Data are provided as two data types. The first type is best-suited for tropospheric water vapour distribution studies disregarding different isotopologues (comparison with radiosonde data, analyses of water vapour variability and trends, etc.). The second type is needed for analysing moisture pathways by means of H2O, δD-pair distributions.

Angesichts der messtechnischen Fortschritte der vergangenen Jahrzehnte und der neu geschaffenen M��glichkeiten, die sich mit den Fourier-Transform Spektrometern der neuesten Generation im Hinblick auf die Messgenauigkeit bieten, steigen auch die Anforderungen an die Auswertung atmosph��rischer Messungen der bodengebundenen Fernerkundung. Um diesen Anforderungen gerecht zu werden, muss das Verst��ndnis ��ber die Wechselwirkung elektromagnetischer Strahlung mit den Spurengasen der Erdatmosph��re und deren Absorptionseigenschaften erweitert werden. Mit hochaufgel��sten Labormessungen, die am Institut f��r Methodik der Fernerkundung (IMF) des Deutschen Zentrums f��r Luft- und Raumfahrt (DLR) in Oberpfaffenhofen aufgenommen wurden, konnten die Voraussetzungen f��r eine Verbesserung der spektroskopischen Parameter von Methan im mittleren Infrarotbereich geschaffen werden. Hierf��r wurde ein Fourier-Transform Spektrometer der Firma Bruker Optics (Bruker IFS125HR) eingesetzt, das mit einer direkt am Spektrometer angebrachten Langweggaszelle betrieben wurde. Diese Multireflexionszelle wurde eigens f��r Zellenmessungen mit einstellbarem Absorptionsweg entwickelt und konnte zudem ��ber einen geregelten Heiz- bzw. K��hlkreislauf auf eine zuvor definierte Temperatur gebracht werden. Aufgenommen wurden Hintergrundmessungen, Absorptionsmessungen mit reinem Methan sowie Messungen mit einer Methan-Luft-Mischung, die lediglich einen geringen Methananteil aufwiesen. Sowohl die Rein-Methan-Messungen als auch die Methan-Luft-Messungen wurden bei Raumtemperatur sowie bei hohen und tiefen Temperaturen mit unterschiedlichen Gesamtdr��cken durchgef��hrt, die in groben Z��gen den zu erwartenden Dr��cken, Temperaturen und Mischungsverh��ltnissen in der Atmosph��re entsprechen. Ausgehend von den daraus hervorgehenden Transmissionsspektren und den Absorptionsparametern f��r Methan, die der HITRAN-Datenbank f��r atmosph��rische Spurengase entnommen wurden, konnte zun��chst eine vorl��ufige Linienliste erstellt werden, deren Anfangswerte zum Teil mithilfe der Spektroskopiesoftware MIRS korrigiert werden mussten. Zudem musste die Parameterliste um zahlreiche Absorptionslinien erg��nzt werden, die zwar in den Messspektren beobachtet aber nicht in der vorhandenen Linienliste zugeordnet werden konnten. Diese Parameterliste bildete dann den Ausgangspunkt dieser Arbeit, die eine verbesserte Methan-Linienliste f��r die bodengebundene atmosph��rische Fernerkundung zum Ziel hat. F��r die Auswertung der gemessenen Transmissionsspektren wurde eine Retrieval-Software entwickelt, die auf der Methode der kleinsten Quadrate basiert und eine ��ber die Voigt-Funktion hinaus gehende Profilfunktion einsetzt. Diese Software erlaubt den simultanen Einsatz mehrerer Spektren bei gleichzeitiger Anpassung mehrerer Linien und Profilparameter in einem Durchlauf. Die implementierte Profilfunktion entspricht im Wesentlichen der Hartmann-Tran-Funktion, die allerdings auf die qSDR-Profilfunktion reduziert wurde und zudem um eine Line-Mixing-N��herung erster und zweiter Ordnung erweitert wurde. Nachdem in einem ersten Schritt neben den Linienpositionen und -intensit��ten die Selbst-Parameter und das Line-Mixing erster Ordnung (Dispersionsanteil) mitsamt deren Temperaturabh��ngigkeiten an die Transmissionsspektren mit reinem Methan angepasst wurden, konnten anschlie��end die Fremd-Parameter sowie die entsprechenden Line-Mixing-Parameter erster und zweiter Ordnung bei Raumtemperatur bearbeitet werden. Abschlie��end wurde die Temperaturabh��ngigkeit der Fremd-Parameter bestimmt, die aus den Methan-Luft-Messungen bei hohen und tiefen Temperaturen gewonnen wurden. In einem Bereich zwischen 2400 und 3000 cm���1 konnten auf diese Weise die Intensit��ten, Positionen und Selbst-Parameter von ann��hernd 30000 Spektrallinien ermittelt werden, deren Linienintensit��ten gr����er als 2��10���26 cm/molecule waren. Zu diesen Linien z��hlten allerdings auch etwa 3500 meist schwach absorbierende Linien, die neu in die Methan-Linienliste mit aufgenommen wurden und h��chstwahrscheinlich den fehlenden Linien der hei��en Banden in der HITRAN-Linienliste zuzuordnen sind. Diese Annahme wird durch die unteren Energieniveaus best��rkt, die bei den neu hinzugef��gten Linien mitgefittet und ansonsten bei den restlichen Linien konstant gehalten bzw. unver��ndert belassen wurden. Aufgrund der starken Druckverbreiterung in den Methan-Luft-Messungen konnte jedoch die ��berwiegende Mehrheit der Absorptionslinien in den Transmissionsspektren nicht mehr aufgel��st werden, sodass die Fremd-Parameter von lediglich 8700 Linien mit Intensit��ten gr����er als 10���24 cm/molecule korrigiert wurden. Ein Vergleich der neuen Profilparameter mit den unver��nderten HITRAN-Werten zeigt, dass die Linienpositionen und -intensit��ten f��r bestimmte Vibrations��berg��nge und Rotationsquantenzahlen deutliche Unterschiede aufweisen. Die Differenzen k��nnen mitunter mehrere Wellenzahlen in der Linienposition bzw. ein bis zwei Gr����enordnungen in der Linienintensit��t betragen. Zudem konnten die Parameter der druckinduzierte Selbst-Verbreiterung bestimmter Vibrationssymmetrien der hei��en Banden insofern verbessert werden, als dass die neuen Parameterwerte nun dem Verlauf der Parameterwerte der kalten Banden folgen und mit steigender Rotationsquantenzahl vorwiegend abnehmen (und nicht wie zuvor zunehmen). Neben der Linienposition und -intensit��t wurden insgesamt 9 Selbst-Parameter und 13 Fremd-Parameter f��r die Anpassung der synthetischen Spektren an die gemessenen Transmissionsspektren eingesetzt. Zu den Selbst-Parametern z��hlten die druckinduzierte Verbreiterung, Verschiebung, Verj��ngung, Verformung, der Dicke-Parameter sowie das Line-Mixing erster Ordnung mitsamt deren Temperaturabh��ngigkeiten. Bei den Fremd-Parametern wurden zudem die Parameter f��r die Line-Mixing-N��herung zweiter Ordnung sowie deren Temperaturabh��ngigkeiten ber��cksichtigt. F��r alle Labormessungen gilt, dass die Residuen mit der erweiterten Profilfunktion und den zus��tzlich zur Verf��gung stehenden Parametern ��ber den gesamten Spektralbereich mitunter deutlich gesenkt werden konnten. Eine Anwendung der neuen Methan-Linienliste auf Atmosph��renmessungen ausgew��hlter Messstationen der bodengebundenen Fernerkundung hat gezeigt, dass die Residuen innerhalb der eng bemessenen NDACC-Fenster sowie in ausgew��hlten breitbandigen Fenstern, ebenfalls deutlich reduziert werden. Zudem wurden die Gesamts��ulen, die vertikale Profile und Jahresg��nge, die jeweils mit der neuen Methan-Linienliste und der unver��nderten HITRAN-Linienliste sowie den NDACC-Fenstern ausgewertet wurden, miteinander verglichen. Die Unterschiede in der Gesamts��ule k��nnen hierbei bis zu ein Prozent betragen, w��hrend die vertikalen Profile in den bodennahen Regionen im Mittel einen kleineren Gradienten aufweisen als zuvor. Insgesamt kann festgestellt werden, dass die neu erstellte, verbesserte Linienliste f��r Methan den gestiegenen Anforderungen an die Auswertung bodengebundener Fernerkundung grunds��tzlich gerecht wird.

Tropospheric water vapour isotopologue distributions have been consistently generated and quality filtered for 12 globally distributed ground-based FTIR sites. The products are provided as two data types. The first type is best-suited for tropospheric water vapour distribution studies. The second type is needed for analysing moisture pathways by means of {H2O,δD}-pair distributions. This paper describes the data types and gives recommendations for their correct usage. E. Sepúlveda is supported by the Ministerio de Economía y Competitividad from Spain under the project CGL2012-37505 (NOVIA project). The measurements in Mexico (Altzomoni) are supported by UNAM-DGAPA grants (IN109914, IN112216) and Conacyt (239618, 249374). Start-up of the measurements in Altzomoni was supported by International Bureau of BMBF under contract no. 01DN12064. 15 Special thanks to A. Bezanilla for data management and the RUOA program (www.ruoa.unam.mx) and personnel for helping maintaining the station. Measurements at Wollongong are supported by the Australian Research Council, grant DP110103118. This study has been conducted in the framework of the project MUSICA which is funded by the European Research Council under the European Community’s Seventh Framework Programme (FP7/2007-2013) / ERC Grant agreement number 256961.

We present lower/middle tropospheric column-averaged CH4 mole fraction time series measured by nine globally distributed ground-based FTIR (Fourier transform infrared) remote sensing experiments of the Network for the Detection of Atmospheric Composition Change (NDACC). We show that these data are well representative of the tropospheric regional-scale CH4 signal, largely independent of the local surface small-scale signals, and only weakly dependent on upper tropospheric/lower stratospheric (UTLS) CH4 variations. At Ny-Ålesund and Izaña, the FTIR work has received funding from the European Community’s Seventh Framework Programme ([FP7/2007–2013]) under grant agreement no. 284421 (see Article II.30. of the Grant Agreement). At Izaña has also received funding from the Ministerio de Economía and Competitividad from Spain for the project CGL2012-37505 (NOVIA project). This study has strongly benefited from work made in the framework of the project MUSICA, which is funded by the European Research Council under the European Community’s Seventh Framework Programme (FP7/2007–2013)/ERC grant agreement number 256961.

We present lower/middle tropospheric column-averaged CH4 mole fraction time series measured by nine globally distributed ground-based FTIR (Fourier transform infrared) remote sensing experiments of the Network for the Detection of Atmospheric Composition Change (NDACC). We show that these data are well representative of the tropospheric regional-scale CH4 signal, largely independent of the local surface small-scale signals, and only weakly dependent on upper tropospheric/lower stratospheric (UTLS) CH4 variations. At Ny-Ålesund and Izaña, the FTIR work has received funding from the European Community’s Seventh Framework Programme ([FP7/2007–2013]) under grant agreement no. 284421 (see Article II.30. of the Grant Agreement). At Izaña has also received funding from the Ministerio de Economía and Competitividad from Spain for the project CGL2012-37505 (NOVIA project). This study has strongly benefited from work made in the framework of the project MUSICA, which is funded by the European Research Council under the European Community’s Seventh Framework Programme (FP7/2007–2013)/ERC grant agreement number 256961.

A new fitting tool for analysis of multiple molecular absorption spectra utilizing a microwindow-based line-by-lineapproach has been developed. Its capabilities include the choice of numerous different line shape models, from a simple Voigt to more sophisticated models like a speed-dependent Galatry including line-mixing. A comfortable manual mode as well as a fully automatic mode have been implemented including various quality assessment procedures like the monitoring of correlation coefficients or the supply of useful information e.g. needed for file cuts (single spectrum residuals). As a first application the new tool is used to re-analyze water vapor absorption spectra in the 1250-1750 cm range. The measurements include pure water as well as water/air-mixture measurements and cover a wide range of column densities. The total air pressure and partial pressure ranges were 50-1000 mb and 0.001-5 mb, respectively. Whereas the original analysis was based on single spectrum fits applying the Voigt procedure, in the present multispectrum fit the speed-dependent Voigt lineshape was used. The advantages of a multispectral analyis approach as well as the need for consideration of narrowing effects is illustrated by the presentation of differences in residuals as well as resulting line parameters for selected transitions. As indicated in opaque as well as non opaque lines could be fitted with the speed-dependent Voigt while the pure Voigt yields to narrow opaque lines.